塔西南坳陷油气藏模式及其形成条件初探

PRIMARY STUDY ON RESERVOIR PATTERN AND ITS FORMING CONDITION IN SOUTHWEST DEPRESSION OF TARIM BASIN

塔西南坳陷是一个经长期发展形成的复合型前陆坳陷。二叠纪后的各次运动，特别是新生代的喜马拉雅运动使天山、昆仑山先后隆升，并发生向盆地的冲断作用，从而使前陆坳陷形成大规模的逆冲断裂和与断层相关的褶皱，与隆升、褶皱、冲断有关的多种类型圈闭，在油气来源充足的情况下可形成多种类型的油气藏。古生界圈闭发育程度较差，中、新生界以发育挤压背斜、断背斜、断层、岩性圈闭为主。无论是古生界油气藏，还是中、新生界油气藏，其形成的关键因素是有断层直接或间接地将油源层和储层联系起来，以提供油气藏形成所需的油气来源，否则再好的圈闭也难以形成油气藏。

Southwest depression in Tarim basin is a complex foreland type as a result of long-term evolution. Each movement after Permian,especially Himalayan movement in Cenozoic caused Tianshan and Kunlun mountains successively elevate and overthrust toward the basin,thereby resulting in large scale thrust faults and fault-related folds in foreland depression.Various traps related with the uplift,fold and thrust fault may form different reservoir types if there was enough oil and gas supply.Paleozoic traps occur in small amounts in which anticline,fault,lithologic and stratigraphic unconformity reservoirs are dominant.Meso-Cenozoic traps occur in large amounts in which compaction anticline,fault-anticline,fault and lithologic reservoirs are dominant.The key to the formation of Paleozoic and Meso-Cenozoic reservoirs is that the source rock is directly or indirectly communicated with the reservoir through the fault.Otherwise,it is difficult to discover oil and gas even in the best-quality traps.